Vascular recruitment

Vascular recruitment is the increase in the number of perfused capillaries in response to a stimulus. I.e., the more you exercise regularly, the more oxygen can reach your muscles.

Vascular recruitment may also be called capillary recruitment.

## Contents

* 1 Vascular recruitment in skeletal muscle
* 2 Vascular recruitment in the lung
* 3 Vascular recruitment in the brain
* 4 Controversy
* 5 References

## Vascular recruitment in skeletal muscle

The term «vascular recruitment» or «capillary recruitment» usually refers to the increase in the number perfused capillaries in skeletal muscle in response to a stimulus. The most important stimulus in humans is regular exercise.[1][2] Vascular recruitment in skeletal muscle is thought to enhance the capillary surface area for oxygen exchange and decrease the oxygen diffusion distance.[citation needed]

Other stimuli are possible. Insulin can act as a stimulus for vascular recruitment in skeletal muscle. This process may also improve glucose delivery to skeletal muscle by increasing the surface area for diffusion. That insulin can act in this way has been proposed based on increases in limb blood flow and skeletal muscle blood volume which occurred after hyperinsulinemia.[3][4][5]

The exact extent of capillary recruitment in intact skeletal muscle in response to regular exercise or insulin is unknown, because non-invasive measurement techniques are not yet extremely precise.[6]

Being overweight or obese may negatively interfere with vascular recruitment in skeletal muscle.[7]

## Vascular recruitment in the lung

Vascular recruitment in the lung (i.e., in the pulmonary microcirculation)[8] may be noteworthy to healthcare professionals in emergency medicine, because it may increase evidence of lung injury,[9] and increase pulmonary capillary protein leak.[10]

## Vascular recruitment in the brain

Vascular recruitment in the brain is thought to lead to new capillaries and increase the cerebral blood flow.[11][12][13]

## Controversy

The existence of vascular recruitment in response to a stimulus has been disputed by some researchers.[14] However, most researchers accept that vascular recruitment exists.[15]

## References

1. ↑ Vascular recruitment in forearm muscles during exercise. Palm T, Nielsen SL, Lassen NA. Clin Physiol. 1983 Oct;3(5):445-51.
2. ↑ Capillary recruitment in exercise: rate, extent, uniformity, and relation to blood flow. Honig CR, Odoroff CL, Frierson JL. Am J Physiol. 1980 Jan;238(1):H31-42.
3. ↑ Vascular recruitment in skeletal muscle during exercise and hyperinsulinemia assessed by contrast ultrasound. Dawson D, Vincent MA, Barrett EJ, Kaul S, Clark A, Leong-Poi H, Lindner JR. Am J Physiol Endocrinol Metab. 2002 Mar;282(3):E714-20.
4. ↑ Direct evidence for insulin-induced capillary recruitment in skin of healthy subjects during physiological hyperinsulinemia. Serné EH, IJzerman RG, Gans RO, Nijveldt R, De Vries G, Evertz R, Donker AJ, Stehouwer CD. Diabetes. 2002 May;51(5):1515-22.
5. ↑ Physiologic hyperinsulinemia enhances human skeletal muscle perfusion by capillary recruitment. Coggins M, Lindner J, Rattigan S, Jahn L, Fasy E, Kaul S, Barrett E. Diabetes. 2001 Dec;50(12):2682-90.
6. ↑ Non-invasive study of pulmonary vascular recruitment during exercise. Bougaci N, Costes F, Bertoletti L. Rev Pneumol Clin. 2010 Jun;66(3):173-8. French.
7. ↑ Visceral and truncal subcutaneous adipose tissue are associated with impaired capillary recruitment in healthy individuals. de Jongh RT, Ijzerman RG, Serné EH, Voordouw JJ, Yudkin JS, de Waal HA, Stehouwer CD, van Weissenbruch MM. J Clin Endocrinol Metab. 2006 Dec;91(12):5100-6.
8. ↑ Physiology of pulmonary capillary recruitment. Wagner WW Jr, Hervé P. Rev Mal Respir. 1989;6(1):39-44. French.
9. ↑ Vascular recruitment increases evidence of lung injury. Ehrhart IC, Orfanos SE, McCloud LL, Sickles DW, Hofman WF, Catravas JD. Crit Care Med. 1999 Jan;27(1):120-9.
10. ↑ Effects of pulmonary vascular recruitment on gamma scintigraphy and pulmonary capillary protein leak. Sugerman HJ, Tatum JL, Strash AM, Hirsch JI, Greenfield LJ. Surgery. 1981 Aug;90(2):388-95.
11. ↑ Concurrent vasculogenesis and neurogenesis from adult neural stem cells. Ii M, Nishimura H, Sekiguchi H, Kamei N, Yokoyama A, Horii M, Asahara T. Circ Res. 2009 Oct 23;105(9):860-8.
12. ↑ What is the blood–brain barrier (not)? Bechmann I, Galea I, Perry VH. Trends Immunol. 2007 Jan;28(1):5-11.
13. ↑ Evidence that heterogeneity of cerebral blood flow does not involve vascular recruitment. Williams JL, Shea M, Jones SC. Am J Physiol. 1993 May;264(5 Pt 2):H1740-3.
14. ↑ Counterpoint: There is not capillary recruitment in active skeletal muscle during exercise. Poole DC, Brown MD, Hudlicka O. J Appl Physiol. 2008 Mar;104(3):891-3.
15. ↑ Point: There is capillary recruitment in active skeletal muscle during exercise. Clark MG, Rattigan S, Barrett EJ, Vincent MA. J Appl Physiol. 2008 Mar;104(3):889-91.

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